Signal delay systems



Jan. 15, 1963 E. E TURNER 3,074,048

SIGNAL DELAY SYSTEMS original Filed Feb. 12, 1951 2 sheets-sheet 1 /Nl/ENTOR FDW/N5. 7Bm/e T REY Jan. 15,V 1963 E. EA TURNER SIGNAL DELAY SYSTEMS 2 Sheets-Sheet 2 Original Filed Feb. 12, 195] Bsliiii Patented Jan. i5, i963 3,074,648 SGNAL DELAY SYSTEMS Edwin E. Turner, West Roxbury, Mass., assigner to Raytheon Company, Lexington, Mass, a corporation of Deiaware Continuation ot' application Ser. No. 210,544), Feb. 12, 195i. This application Mar. Ztl, 1959, Ser. No. 800,897

This is a continuation of my copending application, Serial No. 210,540, tiled February l2, 1951, and now abandoned.

This invention relates to improvements in electronscanning systems, and more particularly to scanning systems ofthe echo-ranging type.

In the copending application, Serial No. 14,017, now Patent No. 2,786,193, tiled March l0, 1948, by Stanley R. Rich, there is disclosed an echo-ranging system wherein a plurality of substantially unidirectional transducers are permanently fixed in the same positions relative to each other. By phasing the operation of said transducers, the overall transducer system may be made to operate as a directional system, that is, one having directional receiving or propagating characteristics.

The aforementioned application discloses a particular electrical system particularly adapted to accomplish the phasing of the transducers so th t they will operate with any of a plurality of desired directivities. Briefly, this is accomplished by feeding an electrical delay line system from each transducer. Energy is coupled from each of the delay lines at Various points along their lengths corresponding to various delayed periods. A pluralit3 of circuits are fed by the energy coupled from each of said delay lines, each circuit being fed energy from each of the delay lines. The delays of the energy feeding the circuits are phased such that each circuit will produce a signal at its output in response to impingement of a signal on the transducer elements from a particular direction, each circuit being responsive to signals from a different direction. As a result, by selecting the output of a particular circuit, any desired directivity of the transducer system may be had.

ln order to successively connect the outputs of each of the circuits to an indicating device, a switching tube is used, said switching tube comprising, for example, a plurality of electrodes, each electrode being successively struck by a beam. The output of said switching tube is, therefore, successively the outputs of each of the circuits. This output is fed to the indicating means as, for example, the grid of a cathode-ray tube, the beam of which is rotated in synehronism with the beam of the switching tube. Thus, the appearance of a signal at the transducer system from any direction will produce a signal at the output of one of the circuits, depending on the direction of the received signal and will produce a bright spot on the cathode-ray tube screen whose angular position indicates the direction of the received signal This invention discloses the use of electromechanical delay lines in place of the electrical delay lines in the systern described in the aforementioned application. By the use of electromechanical delay lines, the delay line system may be greatly simplified and made considerably less expensive and less bulky.

While any desired mechanical delay line system may be used in this system, this invention particularly discloses the use of a novel type of electromechanical delay line. r[his delay line uses as its delaying medium piezoelectrical material, so that signal energy may be coupled out of the delay line at any point along the length thereof by merely contacting said delay line with conductive electrodes.

rThis invention further discloses a particular piezoelectric delay line wherein the transducer is made unitary with the delay line proper, thereby eliminating the necessity of electrical connections between the transducer and the delay line.

This invention further discloses a particular type of piezoelectric delay line wherein the piezoelectric material comprises an elongated cylinder having at the axis thereof a conductive electrode. The signals in such a delay line may be coupled into or out of said delay line `by merely attaching a conductive band around the delay line at the desired point, and the signal will then appear between the central axial electrode and the band surrounding the piezoelectric material.

Other and further objects and advantages of this invention will be apparent as the description thereof progresses, reference being had to the accompanying drawings, wherein:

FIG. l illustrates an echo-ranging system utilizing the mechanical delay line network;

FIG. 2 illustrates a particular delay network wherein each trausducing element is made unitary with its respective delay line;

FIG. 3 illustrates a cross-sectional View of the delay line illustrated in FG. 2, taken along line 3--3 of FIG. 2; and

FIG. 4 illustrates a coaxial piezoelectric delay line.

Referring now to FIG. l, there is shown a plurality or" transducer elements lil which may be of any desired type such as crystal transducers or magnetostrictive transducers. As shown here, these transducers are arranged in a semicircular pattern, and comprise one half of a transducer system which will be described herein. The other half of the transducer system is indicated in dotted outlines and would feed a second delay network similar to the delay network fed by the transducers lil. One side of each of the transducers 1t?, as shown here, is connected to ground, and the other side of each of the transducers is connected, respectively, to electrodes 1l through 1S, respectively, which are in Contact with piezoelectric delay lines 19 through 26, respectively, on one side adjacent one end thereof. On the opposite side of delay lines 19 through 26 are electrodes 27 through 34, respectively, which are grounded, said electrodes cooperating with electrodes 1l through 1S, respectively, to couple energy into Ithe respective delay lines. Delay lines 19 through 25 may be of any desired electromechanical type such as mercury delay lines, magnetostrictive delay lines, or, as shown here, a delay line made up of piezoelectric material. This piezoelectric material may be, for example, barium titanate crystals held together in the desired shape by a binder or molding under pressure and/or heat. lt is to be clearly understood that the piezoelectric material may be any of the other well-known piezoelectric materials such as Rochelle salt crystals.

The other end of each of the delay lines 19 through 26 from the input electrodes 11 through 13 is terminated by being in physical contact with material which absorbs compressional wave energy, as at 35'. Material 35 may be any of the well-known sound absorbing materials such as bodies of cork wool or putty-like plastics. A particular useful sound absorber of the putty-like plastic variety is commercially available under the trade name Viscaloid produced by the General Electric Company.

Spaced aiong each of the delay lines 19 through 26 between the input electrodes 1l through i8 and the absorbing termination 35 is a plurality of signal pick-ott electrodes. These signal electrodes are arranged in groups, each group comprising two pairs of pick-off electrodes, each pair of each group of electrodes picking olf a signal from the delay lines having substantially the same signal time delay, but the signal time delay of electrodes 'pressional wave energy.

picked off for different groups being substantially different. Because the transducer elements are arranged in a semicircular pattern, the spacing between successive groups of electrodes along the delay line decreases in accordance with a sine or cosine function of the angular displacement of successive transducer elements l@ from a reference.

ln order to reduce the side lobes in the directivity pattern of the transducer system comprising transducers lll, 'the signal pick-oil electrodes increase in size toward the more delayed end of the delay lines 19 through 26, with the result that a larger portion of the signals from the transducers lil upon which the instant wave lirst impinges Will appear in the output circuits which correspond to the directivity of Athe impinging wave.

The groupV of signal pick-oi electrodes are interconnected in series circuits similar to the circuits described in the aforementioned copending application, each circuit having one end thereof grounded, and the other end thereof connected, respectively, to a diflerent one of a plurality of circularly arranged electrodes 36 of a switching tube 37. In the interconnections of the electrodes, the lines at the bottom and top of the delay line system are interconnected with lines labeled by like letters being directly connected together by conductors not shown on the drawings.

Switching tube 37 is shown' here diagrammatically as a plurality of electrodes 36 successively contacted by an arm 38 which, in practice, may be an electron beam in an evacuated envelope. The signals appearing at electrodes 36 are successively connected by arm 3S to the input of an amplier 39, the output of which tfeeds the grid 40 of a cathode-ray tube indicating device 4l. The deflection system of the cathode-ray tube 4l comprises coils 42 which are rotated in synchronism with the arm 3S by means of a synchronized beam rotator 43.

A deflection voltage is applied to the coils 42 by means of a sweep generator 4l which may generate a voltage of the type which will produce a substantially linear deilection or" the beam radially outward from the center of the cathode-ray tube screen. Thus, if the sweep generator i4 is triggered simultaneously with the initiation of a short burst of radiation from a transmitting transducer, not shown,y the cathode-ray tube beam will be slowly deflected outward [from the center of the cathoderay tubeV and simultaneously rapidly rotated successively presenting echo signals directively picked up by the transducer and delay line system, and resulting in a plane position indication of surrounding targets which produce echo signals upon impingement of a transmitted signal thereon.

{eferring now to FlGS. 2 and 3, there is shown a modification of the transducer and delay line system shown in FIG. l. In' particular, there is illustrated a horn-shaped transducer element 1d which, as shown here, is made of piezoelectric crystal material, but in reality may be any desired material or medium capable of transmitting com- YThe large end of t-he horn is in contact with the medium from which sign-als are to be received such as, for example, in underwater sound appli# cations, the water. The small end or" the horn' is directly attached to an elongated piezoelectric materiald which g comprises the delay line. Electrodes d6 are positioned at the desired points along Kthe delay line to pick olf the signals with the desired delay which yare phased by an any desired material and shape, the horn shape illustrated herein' being merely for purposes of illustration.

Furthermore, if desired, the signal energy may travel down the delay line material as transverse Waves. For optimum pick-ott conditions, the electrodes 46 should be positioned parallel to the amplitude vector of the wave.

Referring now to FIG. 4, there is shown a further modiiication ot a piezoelectric delay line wherein the delay line material 45 is in the form of a cylinder. Extending coaxially down' the center of the cylinder is a conductive member 47 which acts as a common electrode for all the signal input and output electrodes. Signal input and output electrodes 48 may then be, as shown, rings surrounding the piezoelectric delay line material 45 in contactV therewith. The energy lfrom the transducers lll is then lfed into the delay line material by application between the common conductor 47 and the signal input electrode at one end of the delay line material 4S, thereby setting up compressional wave signals in the material 45 which are propagated toward the other end thereof, and are to be absorbed by the absorbing material 35. These waves which will comprise substantially longitudinal compressional waves may lthen ybe picked oit by signal pick-olf electrodes t3 spaced along the delay line material 45 and used to produce delayed output signals.

While the systems of FIGS. l and 2 show the interconnections between the electrodes in the form of series circuits of electrodes, the modification of FlG. 4 is adapted for an interconnection system where the electrodes of each circuit are in parallel. The use of barium titanate for the delay material is particularly useful with circuits `wherein the pick-olf electrodes are connected in series since the electric impedance of the barium titanate is relatively low so lthat the overall impedance of a series circuit will not be in excess of the load comprising 4the switch 37 into which the circuits feed.

This completes the description of the embodiments of the invention illustrated herein. However, many modications .thereof will be apparent to persons skilled in the art without departing from the spirit and scope or" this invention. For example, the number of transducer elements lll and the delay lines may be varied greatly. ln fact, twenty-four were used with each delay network in practice. Other indicating systems besides the cathoderay tube presentation may be employed, and the piezoelectric delay lines may be used for other purposes such interconnection between diierent delay lines in a manner ,Y

' up longitudinal compressional waves in the horn material which will be propagated strom the little end of the horn The other end ofY along the delay line material 45 and picked oil by thc Y electrode. lt is to be clearly understood that the transducers l@ attached to the delay line material may be of as computer or communications work. Accordingly, it is desired that this invention be not limited by the description of the embodiments of the invention illustrated herein, except as defined by the appended claims.

t Wha-t is claimed is:

1. A system comprising a group of wave energy propai -to a predetermined directivity of said latter group, theV delay introduced by said delay lines differing between said transducerV elements, wherebysignals of .varying phase from said transducer elements into said piezoelectric del-ay lines appear in phase at said selected intervalsialong said delay line. Y

A3. A system comprising a group of compressional wave energy transducer'e'lernents spaced in a xed pattern, a

plurality of signal channels interconnecting said elements, said channels comprising'solid piezoelectricrdelay lines, and means comprising a plurality of outputs for progressively selecting a particular channel dependent upon the desired signal phase relation of energy passing through said transducer elements, whereby input signals of varying phase from said transducer elements into said solid delay lines are made to appear in phase at said selected outputs.

4. A system comprising a group of compressional wave energy propagating elements spaced in a xed pattern, and a plurality of signal channels interconnecting said elements, said channels comprising solid piezoelectric delay lines directly coupled with compressional wave energy transfer means to said elements.

v5. A system comprising a group of electromechanical vibratory elements spaced in a fixed pattern, a plurality of signal channels connected to said elements, said channels comprising unitary piezoelectric delay lines, and means for selecting Va particular channel dependent upon the desired signal phase relation of energy passing through said transducer elements.

6. An electromechanical signal delay line comprising a plurality of bodies of piezoelectric material, signal input means in contact with one portion of each body, and a plurality `of substantially equal spaced pairs of signal out. put means interconnected and in contact with other spaced portions of each body.

7. A system comprising Ia group of sonic electromechanical unitary vibratory delay elements, signal input means connected to said elements, signal output channels connected to said elements, means for selecting a .particular signal output channel, and means for indicating a signal obtained from a selected channel.

8. A system comprising a group of sonic electromechanical unitary elements, signal input means connected to said elements, a signal output circuit coupled to each of said elements, and switching means for sequentially selecting each of said output circuits.

9. An electromechanical signal delay line comprising a plurality of bodies of piezoelectric material, electrode means for introducing a compressional Wave signal having a predetermined phase pattern into each body, and electrode means interconnected and spaced `along said bodies for extracting the pattern of said signal from said bodies.

10. An electromechanical signal delay line comprising a plurality of bodies of piezoelectric material, signal input electrodes in contact with one portion of each body introducing a signal of predetermined phase pattern into said bodies, and interconnected electrode means for extracting said signal from said bodies.

11. An electromechanical signal delay line comprising a plurality of bodies of homogeneous piezoelectric material, signal input electrodes in contact with one portion of each body, and a plurality of signal output electrodes in contact with other spaced portions of each body and interconnected to provide a predetermined delay.

12. An electromechanical signal delay line comprising a plurality of elongated rods of homogeneous piezoelectric material, signal input electrodes in contact with one portion of said rods on opposite sides of the longitudinal axis thereof, and a plurality of pairs of signal output electrodes in contact with other spaced portions of said rods on opposite sides of the longitudinal axis thereof `and interconnected to provide a predetermined delay.

13. An electromechanical signal delay line comprising an elongated body of piezoelectric material, a central electrode surrounded by said body land coaxial therewith, and a plurality of annular electrodes encircling said body.

14. A system comprising a group of Wave energy transducer elements arranged in a xed pattern, one of a group of compressional wave energy delay lines connected, respectively, to each of said transducer elements, said delay lines comprising a body of piezoelectric material, signal input means in contact with one portion of said body, signal output means in contact with another portion of said body, and `a plurality of output signal channels fed by said delay lines.

15, A system comprising a group of wave energy transducer elements, a plurality of signal channels interconnecting said elements, each of said channels comprising a unitary body of piezoelectric material, signal input means in contact with one portion of said body, a plurality of signal output means in contact with other portions of said body, and a plurality of output signal channels fed by said signal output means.

16. A system comprising a group of wave energy transducer elements, `a plurality of signal channels interconnecting said elements, each of said channels comprising an elongated body of piezoelectric material, signal input means in cont-act lwith one portion of said body, signal output means in contact with other portions of s-aid body, and means comprising a plurality of said output means for selecting a particular channel dependent upon the desired signal phase relation of said transducer elements.

17. A system comprising a plurality of electromechanical unitary vibratory rods including input and output transducer means cooperating with each of said rods, signal input means connected to said input transducer means, a plurality of signal output means connected to said output transducer means, and commutator-type switching means for sequentially sampling said signal output means.

18. A system comprising a plurality of homogeneous electromechanical vibratory rods, input transducer means comprising field producing means cooperating with one portion of said rods adapted to introduce signal energy into said rods, output transducer means comprising eld producing means cooperating with another portion of said rods for picking off signal energy from said rods, and commutator means having a movable element and a plurality of commutator segments sequentially coupled thereto, each of which segments being coupled to said output transducer means.

19. A system comprising a plurality of electromechanical unitary vibratory elements, signal input means coupled to one portion of said elements and interconnected in a manner adapted to introduce signal energy simultaneously into said elements, signal output means coupled to another portion of said elements, and commutator means coupled to said signal output means.

References Cited in the le of this patent i UNITED STATES PATENTS 1,955,471 yPooler Apr. 17, 1934 1,977,169 Cady Oct. 16, 1934 2,361,998 `Fleming-Williams Nov. 7, 1944 2,570,203' Busignies Oct. 9, 1951 2,640,925 Hirsch June 2, 1953 2,711,515 Mason June 2l, 1955 2,714,708 Howatt et al. Aug. 2, 1955 2,786,193 Rich M-ar. 19, 1957 

3. A SYSTEM COMPRISING A GROUP OF COMPRESSIONAL WAVE ENERGY TRANSDUCER ELEMENTS SPACED IN A FIXED PATTERN, A PLURALITY OF SIGNAL CHANNELS INTERCONNECTING SAID ELEMENTS, SAID CHANNELS COMPRISING SOLID PIEZOELECTRIC DELAY LINES, AND MEANS COMPRISING A PLURALITY OF OUTPUTS FOR PROGRESSIVELY SELECTING A PARTICULAR CHANNEL DEPENDENT UPON THE DESIRED SIGNAL PHASE RELATION OF ENERGY PASSING THROUGH SAID TRANSDUCER ELEMENTS, WHEREBY INPUT SIGNALS OF VARYING PHASE FROM SAID TRANSDUCER ELEMENTS INTO SAID SOLID DELAY LINES ARE MADE TO APPEAR IN PHASE AT SAID SELECTED OUTPUTS. 